A Four-Site Molecular Model for Simulations of Liquid Methanol and Water-Methanol Mixtures: MeOH-4P

In this work, we present a new four-site potential for methanol, MeOH-4P, fitted to reproduce the dielectric constant e, the surface tension γs, and the liquid density ρ of the pure liquid at T = 298.15 K and p = 1 bar. The partial charges on each site were taken from the OPLS/2016 model with the only difference of putting the negative charge on the fourth site (M) instead of on the O atom, as done in four-site water models. The original Lennard-Jones (LJ) parameters of OPLS/2016 for the methyl moiety (Me) were modified for the fitting of ρ and γs, whereas the parameters of the TIP4P-FB water model were used for the O atom without change. Taking into account the energetic cost of the enhanced dipole relative to the isolated molecule, the results from simulations with this model showed good agreement with experiments for ρ, αp, κT, Cp, and ΔHv–l. Also, the temperature dependence of γs and e is satisfactory in the interval between 260 and 360 K, and the critical point description is similar to that of OPLS/...